Semiconductor devices may be highly integrated for satisfying high performance and low manufacture costs. Since integration of the semiconductor devices may be an important factor in determining product price, high integration may be increasingly requested. Integration of typical two-dimensional or planar semiconductor memory devices may be primarily determined by the area occupied by a unit memory cell, such that it may be greatly influenced by the level of technology for forming fine patterns. However, the extremely expensive processing equipment needed to increase pattern fineness may set a practical limitation on increasing the integration of the two-dimensional or planar semiconductor memory devices. Therefore, there have been proposed three-dimensional semiconductor memory devices having three-dimensionally arranged memory cells.